Reduction of dielectric losses through use of organoclay in semiconductor or insulator compositions

Abstract

Organodavs are added to semiconductive compositions to provide a reduction in the dielectric losses of layered composites in which the semiconductive layer contains species which could migrate into the insulation and result in undesirably high dielectric losses, The invention semiconductive compositions provide improved performance in power cable applications.

What is claimed is: 
     
       1. A structure comprising:
 a semiconducting layer comprising a first material that comprises a first polymeric resin and a conductive filler, wherein the first polymeric resin comprises (i) at least one propylene copolymer which is a copolymer of propylene and 12 wt % ethylene, the propylene copolymer comprising lossy species and the propylene copolymer having a peak melting point of 80 C and a melt flow rate of 25 g/10 minutes, (ii) an ethylene/vinyl acetate copolymer, and (iii) from 1 wt % to 3 wt % organoclay, based on the total weight of the polymeric resin in the first material; and, 
 an insulating layer comprising consisting of a second material that consisting of a second polymeric resin and optionally up to 3 wt % of an organoclay based on the total weight of the polymeric resin in the second material, wherein the second polymeric resin consists of a polyethylene crosslinked with dicumyl peroxide, 
 wherein the semiconducting layer and the insulating layer are at least partially in physical contact with each other, and 
 the ratio of AC dielectric losses of a comparative structure to the structure is greater than 1.5, after aging at 140° C. for one week, when measured at a temperature of 130° C. and a frequency of 60 Hz, the comparative structure being identical to the structure except that the comparative structure lacks organoclay. 
 
     
     
       2. The structure of  claim 1  wherein the first polymeric resin further comprises at least one ethylene homopolymer and/or ethylene copolymer. 
     
     
       3. The structure of  claim 1  wherein the conductive filler comprises at least one carbon black compound. 
     
     
       4. The structure of  claim 1  as a cable comprising:
 a core comprising one or more conductors; 
 the semiconducting layer; and, 
 the insulating layer adjacent to the semiconductor layer, wherein the semiconducting layer and the insulating layer directly or indirectly surround the core. 
 
     
     
       5. The cable of  claim 4 , wherein the organoclay is a natural montmorillonite modified with a quaternary ammonium compound. 
     
     
       6. The cable of  claim 4  wherein the first polymeric resin further comprises at least one ethylene homopolymer and/or ethylene copolymer. 
     
     
       7. The cable of  claim 4  wherein the conductive filler comprises at least one carbon black compound. 
     
     
       8. The structure of  claim 4  further comprising a plurality of neutral copper wires wrapped around the insulating layer, the plurality of neutral copper wires forming concentric helices. 
     
     
       9. The structure of  claim 1  wherein the organoclay is a natural montmorillonite modified with a quaternary ammonium compound. 
     
     
       10. The structure of  claim 1  wherein the first polymeric resin is a thermoplastic resin.